The invention relates to a piezo valve which has a plurality of piezoelectric flexural transducers and is adapted for the control of fluid flows.
In the case of a piezo valve disclosed in the patent publication WO 98/25061 two piezoelectric flexural transducers are connected together by means of a flexible contacting strand having electrical conductors and are arranged separately from one another in a valve housing. In accordance with the desired valve function the flexural transducer may be electrically driven in order to cause a deflection movement, which may be applied for opening or closing the valve openings to be controlled.
As in the case of piezo valves comprising only a single flexural transducer with the design in accordance with the said patent publication WO 98/25061 there is the problem that the displacements obtainable by the deflection of the flexural transducers, and accordingly the maximum cross section which may be made available for flow, of a valve opening is relatively small in the case of conventional drive voltages.
One object of the invention is to create a piezo valve in the case of which using one piezo transducer larger displacement movements may be ensured.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention a piezo valve comprises a flexural transducer unit arranged in a valve housing, and which has at least two flexural transducers able to be driven by the application of drive voltages to produce opposite deflection movements, such two flexural transducers being arranged alongside each other with mutually parallel planes of deflection, and being fixedly joined together in a terminal region of the flexural transducer unit with the formation of a common bearing section, at which the flexural transducer unit is pivotally mounted for pivoting around a axis of rotation extending athwart the deflection planes in relation to the valve housing, at least one of such flexural transducers being designed in the form of a control flexural transducer serving for the control of at least one valve opening associated with it, while the other flexural transducers constitutes a support flexural transducer suitable for increasing the displacement and/or the force of the control flexural transducer, and which may be biased against a support face arranged in its displacement path by the application of the drive voltage. In the case of such a design the application of a drive voltage to the flexural transducer unit in a known manner can cause the deflection of the control flexural transducer, this giving rise to a certain displacement movement of such control flexural transducer. By now additionally activating the support flexural transducer, which bears in an opposite direction of deflection on the support face arranged in its displacement path, there will be a pivoting of the remaining flexural transducer unit around the axis of rotation, this leading to an additional displacement of the control flexural transducer in the desired direction of deflection and accordingly an increase in the displacement path which may be produced with it. Additionally or as an alternative the behavior described may also be employed to increase the force, with which the control flexural transducer is held in a given position.
Using only a single control flexural transducer and a single support flexural transducer it is possible to provide a simple shut off valve function, this creating the possibility of producing a 2/2 way valve in conjunction with a further valve opening.
However, the flexural transducers of the flexural transducer unit may if needed be respectively adapted to implement a multiple function so that each flexural transducer represents a control flexural transducer which simultaneously functions as a support flexural transducer for the respectively other control flexural transducer. Accordingly, while sticking the above mentioned advantages as regards increasing the displacement and/or closing force of functionally higher order higher piezo valves may be designed, as for instance 3/2 way and 3/4 way valves, which also have a middle position, in the case of which each flexural transducer closes its associated valve opening. Such piezo valves are important for applications, in which it is a question of shutting down on or trapping a predetermined fluid volume.
A further advantage of the rotary bearing of the flexural transducer unit is that in the case of thermal deformation there is an automatic correction of position or angular setting takes place without influencing stress relationships and so that irrespectively of thermal effects operational properties will always be the same.
Finally the design in accordance with the invention also facilitates the production of the piezo valve, because it is possible to dispense with a clamping in position of the flexural transducer, which only has to be mounted so that it may be pivoted.
Further advantageous developments of the invention are defined in the claims.
If it is a question of producing a reciprocal functionality so that each flexural transducer constitutes both a control flexural transducer and also a support flexural transducer, it is a particular advantage for the support face ensuring the support function to be formed directly by the valve seat of the respectively associated valve opening. It accordingly is possible to do without a separate support face, its function being performed by the valve seat. It is furthermore an advantage if in the case of the presence of two valve openings to be served such valve openings are provided on one and the same side of the flexural transducer unit. This means that production is simplified, because all valve openings to be served and any associated valve seats may be produced in a common part of the valve housing so that manufacturing inaccuracies may be minimized.
Spring means may be present to bias at least one controlled flexural transducer toward the closed position closing the valve opening served and hold same closed when in the electrically deactivated state. By way of the connection, which is torsionally stiff, at the bearing section it is simultaneously accordingly possible to ensure that furthermore the other flexural transducer is biased into a closed position to the extent that it is also designed as a control flexural transducer.
It is convenient for the flexural transducer elements to be so electrically connected together that by joint control thereof a simultaneous deflection in the same direction is caused. It would however also be possible to provide for individual control thereof so that for example the desired effect increasing the displacement and/or force is only used when necessary or a variable switching action takes place, in order to have variable increases in the displacement as for example for continuous applications. In a particularly advantageous design in accordance with the invention of the pivotal bearing the flexural transducer unit has one side of the bearing section placed on an engagement part on the housing and it is biased here by at least one loading element, which acts from the opposite side, against the engagement part. The flexural transducer unit is in this case held at the pivotal bearing point so that it is axially fixed in order to ensure the desired rotary entraining effect. The wording at least one loading element means more particularly a spring element. Given a suitable design of the flexural transducer unit the supply of the drive voltage necessary for operation may be directly by way of the at least one loading element and/or by way of the engagement part so that no additional electrical contact means are necessary.
It is more particularly taking into account the respective operational requirements that it is possible to depart from the equal distance normally present between the valve openings to be served and the axis of rotation and to have different distances here. Furthermore, in the case of there being several valve openings to be served, the valve seat associated with them may be at least approximately in a common plane or at different levels.
The stiff connection between the two flexural transducers at the common bearing section could in principle be produced by any suitable attachment means, which ensure such a stiff connection that between the two flexural transducer transmission of torque is ensured, which leads to the desired entraining effect, in the direction of rotation defined by the axis of rotation. However, as a particularly preferred design it is possible to provide the one or more flexural transducers respectively with at least one piezo body having one or more piezo material layers, such piezo bodies having an associated electrode arrangement, the bodies being integrally connected together at the bearing section with the piezo material layers of their piezo bodies. This integral design is more particularly advantageous from the manufacturing point of view, it being possible to imagine the flexural transducer unit being like a plate or board slotted along part of its length.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the accompanying drawings.